An electric motor commutator is a rotary switch that allows the electric current flowing through an electromagnet in a portion of a DC electric motor to be switched during rotation. This switching produces forces between the rotating portion of the motor and a stationary portion of the electric motor and causes rotation of the motor.
Generally, a commutator is constructed of a ring of wedge-shaped copper bars interspersed with thin insulating sheets of mica. For optimum operation of the motor, it is important that the radial spacing of these segments be consistent all the way around the commutator. This spacing is particularly important in how it relates to the span of the motor.
An exemplary embodiment provides a commutator measurement device with an inspection head for measuring distances along the commutator surface and it may have a rotary encoder adjacent to and in contact with the commutator. The encoder turns as the commutator is turned, and a sensor, such as a fiber optic sensor, is fixedly positioned adjacent to and at a constant distance from the commutator surface. The signals from both the rotary encoder and the fiber optic sensor are transmitted via data transmission cables to a processing system which may include a microprocessor unit electrically interfaced with a computer. The signals are processed by the microprocessor unit and transmitted to the computer for data viewing and further analysis.
In accordance with more specific aspects of the present disclosure, the fiber optic sensor comprises an emitter, a receiver, and a signal amplifier that produces a high or a low output. The signals from both the rotary encoder and the fiber optic sensor are maintained in temporal correlation by a microprocessor unit as the commutator is turned beneath the inspection head.
The rotary encoder measures the distance traveled around the circumference of the commutator by the emission of a predetermined number of electrical pulses per revolution of the encoder wheel, while the fiber optic sensor marks the transitions between the copper bars and the mica sheets with a change between a high signal and a low signal. Data from both the rotary encoder and the fiber optic sensor are maintained in temporal correlation by a programmable microprocessor unit so that each segment transition is marked by a unique number of pulse counts from the rotary encoder. The correlated data is processed and sent to a computer software program for viewing and further analysis.